Retractable safety knife

ABSTRACT

A retractable safety knife has a hollow handle with an opening at an end thereof, a pusher that is movably disposed within the handle and is operable by a user, and a blade that is connected with an end of the pusher. When the pusher moves from a blade-retracted position to a blade-extended position, the blade extends outwardly from the handle opening and rotates from a nested position to an extended position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a retractable safety knife, and moreparticularly, to a apparatus and method for a surgical retractablesafety knife, for both ophthalmic and non-ophthalmic applications, inwhich a blade is retracted within a handle of the knife.

2. Description of the Related Art

In various surgical procedures, the surgeon typically has to make anincision in the patient to remove unwanted tissue, repair damagedtissue, or implant a device to improve the patient's well being. Incertain cases, all three of these activities, or a combination thereof,must be done in a single procedure. For example, in cataract surgery,the surgeon removes a natural, ocular lens that has been clouded by acataract and replaces it with an artificial lens that will improve thepatient's eyesight. To perform this procedure, an incision is made inthe cornea using a scalpel. This provides the surgeon with access to thepatient's natural lens. The clouded lens is cut loose and removed. Thereare a number of different procedures used to remove a patient's lens.Two of the more common techniques are known as extracapsular surgery andphacoemulsification.

In extracapsular surgery, the surgeon removes the lens leaving behindthe back half of the capsule. In phacoemulsification, the surgeonfragments the lens by ultrasonic vibrations and the lens issimultaneously irrigated and aspirated. After the lens is removed, thesurgeon inserts an artificial lens, known as an intraocular lens (IOL),into the eye either behind or in front of the iris. Two C-shaped armsconnected to the IOL eventually become scarred into the side of the eyeand hold the IOL firmly in place.

In another type of ophthalmic procedure known as the Implantable ContactLens procedure (ICL), the surgeon makes an incision in the patient's eyeand implants a contact lens in the eye in front of the existing lens butbehind the iris. This corrects the patient's vision so that he or shecan see clearly without the need for external contact lenses oreyeglasses.

Typically a nurse or other surgical assistant manages the devices usedduring such delicate surgeries. For example, the assistant ensures thatthe appropriate sterile devices are available in the operating suite forthe particular procedure that is to be performed. With respect toscalpels, the nurse often hands the scalpel to the surgeon in apredetermined orientation so that the surgeon can grip the scalpel'shandle without taking his or her eyes away from the patient. This alsominimizes the possibility that the surgeon may be cut with the blade onthe scalpel. After the surgeon completes the incision, the scalpel ishanded back to the assistant for proper disposal or sterilization. Whilethe procedure is being performed, this requires the assistant to placethe used scalpel on a particular tray that will be removed after theprocedure is completed. The devices on the tray are then disposed of orare sterilized for reuse.

If all appropriate protocols are followed, no hospital personnel will becut by used or unused scalpel blades. Unfortunately, accidental cuts ofhospital personnel do occur for a variety of reasons. For example,because the surgeon and assistant are concentrating on the patient andthe procedure being performed on the patient, they may not pay closeattention to the scalpels. The assistant may put the used scalpels in aninappropriate location or, even if the used scalpels are placed on theproper tray, the blade may be exposed to the operating suite personnel.In these situations, the operating suite personnel may inadvertentlycome into contact with the blade as they move around the patient duringthe procedure and be cut or nicked by an exposed blade.

Other hospital personnel may also come into contact with such blades andmay also be cut or nicked. Usually, used blades are disposed of in anappropriate sharps container that allows used needles and blades to beinserted into the container but prevents access by hospital personnel tothe sharp end of a needle or the sharp cutting surface of the blade.However, during cleanup of the operating suite, the used blades may beexposed prior to their placement in the appropriate sharps container. Ifhospital personnel are not paying close attention to their activities,or if the exposed blades are hidden from view because they are buried ina pile of other devices or hospital linen, these hospital personnel maycome into contact with the sharp cutting surface of the blade and be cutor nicked.

Cuts and nicks from blades are uncomfortable and distracting at best. Inaddition, such cuts and nicks from used blades may result in blood orbody fluid exposure which can result in the spread of infectiousdiseases between the patient and hospital personnel. Concern over thissituation has become especially acute in recent years because of suchdiseases as acquired immunodeficiency syndrome, i.e. AIDS, andhepatitis. These diseases may be transmitted from an infected person toanother person by the transmission of body fluids, typically blood.

Further, the blade of the scalpel must be protected from accidentaldamage prior to intended use.

In view of the need for a scalpel that can at least minimize the chancesof accidental cuts or nicks, while also protecting the cutting edge ofthe blade, numerous scalpels have been designed. These designs typicallytake the form of a scalpel having a guard that shields the sharp cuttingsurface of the blade from undesired contact with hospital personnel andsurrounding surfaces. The guard in these devices can be extended to aposition shielding the blade or retracted exposing the blade for use.Alternatively, the scalpel may be designed to allow the blade to moveinto or out of the scalpel handle, to either shield or expose the sharpcutting surface.

These designs, however, may require attention by the user to shield orexpose the blade. Additionally, the guard (even when transparent) mayvisually distort the handle outline when retracted. Any design thatallows the blade to move, for retraction or extension purposes, alsointroduces design issues regarding exact blade positioning and rigidityduring use. Such issues also apply in cases in which the user isrequired to hold the retracted guard as a grip.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of embodiments of the present invention toprovide a safety knife that protects people from accidental cuts andprotects the blade from accidental damage, as well as affords a clearview of the blade during use, and affords good tactile feedback to auser.

The foregoing and/or other aspects of embodiments of the presentinvention are achieved by providing an apparatus, including a hollowhandle having an opening at an end thereof, a pusher movably disposedwithin the handle and operable by a user, and a blade connected with anend of the pusher. When the pusher moves from a blade-retracted positionto a blade-extended position, the blade extends outwardly from thehandle opening and rotates from a nested position to an extendedposition.

The foregoing and/or other aspects of embodiments of the presentinvention are also achieved by providing an apparatus, including ahollow handle having an opening at an end thereof, and a tilt track; apusher movably disposed within the handle and operable by a user, thepusher comprising a main portion connected with a tilt beam, the tiltbeam having a tilt pin disposed thereon, the tilt pin engaging the tilttrack; and a blade connected with an end of the tilt beam. The tilttrack defines a guide path for the tilt pin during extension andretraction of the blade, to deflect the tilt beam, thereby rotating theblade relative to the handle and translating the blade relative to thehandle.

The foregoing and/or other aspects of embodiments of the presentinvention are also achieved by providing an apparatus, including ahollow handle having an opening at an end thereof, and a tilt track; apusher movably disposed within the handle and operable by a user, thepusher comprising a main portion connected with a tilt beam, the tiltbeam having a tilt pin disposed thereon, the tilt pin engaging the tilttrack; and a blade connected with an end of the tilt beam. When thepusher moves from a blade-extended position to a blade-retractedposition, the tilt pin moves in the slot, deflecting the tilt beam, andthe blade rotates relative to the handle, from an extended position to anested position, and retracts through the handle opening; and/or whenthe pusher moves from the blade-retracted position to the blade-extendedposition, the tilt pin moves in the slot, deflecting the tilt beam, andthe blade extends through the handle opening and rotates from the nestedposition to the extended position.

The foregoing and/or other aspects of embodiments of the presentinvention are also achieved by providing an apparatus, including asubstantially cylindrical handle defining a chamber therein and havingat least one slot extending along a longitudinal axis accessing thechamber, the chamber being open at a distal end of the handle, thechamber having a tilt track disposed therein defining a guide path; apusher movably disposed within the chamber and having a controlmechanism protruding through the longitudinal handle slot, the pushercomprising a main portion connected with a tilt beam, the tilt beamhaving a tilt pin disposed thereon, the tilt pin engaging the tilt trackand being guided along the guide path; and a blade connected with an endof the tilt beam. Moving the pusher control mechanism between opposingends of the longitudinal handle slot translates the main portion of thepusher, moves the tilt pin along the guide path, deflects the tilt beam,and translates and rotates the blade between a nested position,retracted within the chamber, and an extended position external to thechamber, via the distal opening of the handle.

The foregoing and/or other aspects of embodiments of the presentinvention are also achieved by providing a method for shielding andexposing a blade in a surgical instrument, comprising at least one ofrotating the blade relative to a handle of the surgical instrument, froman extended position to a nested position, and retracting the bladethrough a handle opening; and extending the blade through the handleopening and rotating from the nested position to the extended position.

Additional and/or other aspects and advantages of the present inventionwill be set forth in part in the description that follows and, in part,will be apparent from the description, or may be learned by practice ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of embodiments of theinvention will become apparent and more readily appreciated from thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exploded view of a related art safety knife with aretractable guard;

FIGS. 2A and B respectively illustrate the safety knife of FIG. 1 withthe guard in retracted and extended positions;

FIG. 3 illustrates an exploded view of a retractable safety knifeaccording to a first embodiment of the present invention;

FIGS. 4A and B respectively illustrate the retractable safety knife ofFIG. 3 in blade-extended and blade-retracted positions;

FIGS. 5A and B illustrate top and bottom views of a base of the safetyknife of FIG. 3;

FIGS. 6A and B illustrate top and bottom views of a cover of the safetyknife of FIG. 3;

FIG. 7A illustrates a pusher of the safety knife of FIG. 3, and FIG. 7Billustrates a pusher according to another embodiment of the presentinvention;

FIG. 8A illustrates cutaway and end views of an end of a handle of thesafety knife of FIG. 3;

FIG. 8B illustrates cutaway and end views of the pusher, a blade, andthe end of the handle of the safety knife of FIG. 3 in theblade-extended and extended positions;

FIG. 8C illustrates cutaway and end views of the pusher, the blade, andthe end of the handle of the safety knife of FIG. 3 in theblade-retracted and nested positions;

FIG. 9A illustrates enlarged cutaway and end views of the pusher, theblade, and the end of the handle of the retractable safety knife of FIG.3 between the blade-extended/extended positions andblade-retracted/nested positions;

FIG. 9B illustrates enlarged cutaway and end views of the pusher, theblade, and the end of the handle of the retractable safety knife of FIG.3 in the blade-retracted and nested positions;

FIG. 10 illustrates a cutaway view of a modified tilt track according toa second embodiment of the present invention;

FIG. 11A illustrates a cutaway view of the handle and the head showingan annular groove and an annular protrusion according to a thirdembodiment of the present invention, and FIG. 11B illustrates a cutawayview of the handle and the head showing an annular groove and an annularprotrusion according to another embodiment of the present invention;

FIGS. 12A 12E illustrate a modified pusher of a safety knife accordingto a fourth embodiment of the present invention, and an interaction of aslot of the pusher with an alignment pin of the handle; and

FIGS. 13A and 13B respectively illustrate safety knife 10 of FIG. 1 andretractable safety knife 40 of FIG. 3 in position for a typical clearcorneal incision.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments described exemplify the present invention byreferring to the drawing figures.

Solutions to the above-described related art problems can be found incommonly-assigned U.S. Pat. No. 7,022,128 and U.S. patent applicationSer. Nos. 10/828,501 and 11/252,575, all of which are herebyincorporated by reference in their entirety. A device in accordance withthe last-mentioned application is shown in FIGS. 1, 2A, and 2B. FIG. 1illustrates an exploded view of a safety knife with a retractable guard,and FIGS. 2A and B respectively illustrate the safety knife of FIG. 1with the guard in retracted and extended positions.

As shown in FIGS. 1, 2A, and 2B, the safety knife 10 includes a cover 12and a base 14, which together form a hollow handle 16. The base 14includes a blade 18, which in the illustrated embodiment is a bentblade. A pusher 20 is disposed within the handle 16, and includes ashield or guard 22, which selectively covers the blade 18, and a button24, which extends through slot 26 of cover 12. As shown in FIG. 2B, theguard 22 includes an enlarged distal end 28, due to the angled nature ofthe bent blade 18. When a user slides button 24 to a rea of slot 26,guard 22 is retracted, exposing blade 18 for use. And when the userslides button 24 to a front of slot 26, guard 22 slides forward so thatenlarged distal end 28 covers the blade 18, thereby protecting a userfrom an accidental injury, and protecting the blade 18.

While the safety knife 10 accomplishes these goals, in the extendedposition, it may be possible to deflect the guard 22 into the blade.Further, while the enlarged distal end 28 may be made of a transparentmaterial, the curved surface may distort a surgeon's view of the blade18 (see, e.g., FIG. 13B).

FIG. 3 illustrates an exploded view of a retractable safety knifeaccording to an embodiment of the present invention. FIGS. 4A and Brespectively illustrate the retractable safety knife of FIG. 3 inblade-extended and blade-retracted positions. As shown in FIGS. 3, 4A,and 4B, retractable safety knife 40 includes a cover 42, a base 44, apusher 46, and a blade 48. According to one embodiment, the cover 42 andthe base 44 are ultrasonically welded together to form a handle 50.Further, according to one embodiment, the retractable safety knife 40 isdistributed as a product with the pusher 46 and blade 48 in theretracted or safe position.

FIGS. 5A and B illustrate top and bottom views of base 44. Similarly,FIGS. 6A and B illustrate top and bottom views of cover 42. As shown inFIGS. 5A, 5B, 6A, and 6B, according to one embodiment, cover 42 has aplurality of alignment pins 90 and base 44 has a corresponding pluralityof alignment holes or alignment bushings 92. During assembly, thealignment pins 90 are inserted into the alignment bushings 92 to alignthe cover 42 and the base 44 to form the handle 50. According to anotherembodiment, alignment pins 90 are disposed on base 44, and alignmentbushings 92 are disposed on cover 42, According to yet anotherembodiment, alignment pins 90 and alignment bushings 92 are disposed onbase 44, and corresponding alignment bushings 92 and alignment pins 90are disposed on cover 42.

Referring back to FIGS. 3, 4A, and 4B, the handle 50 is substantiallycylindrical, and is hollow to define a chamber therein. Additionally, asbest shown in FIG. 4B, handle 50 has an opening 52 at a distal endthereof, and a slot or opening 54 that extends along a longitudinal axisof the handle 50 and accesses the chamber. As shown in FIG. 4B,according to one embodiment, the opening 52 is substantially circular.Slot 54 has detents 56 and 58, corresponding, respectively, to theblade-extended and blade-retracted positions. According to oneembodiment, detents 56 and 58 are each formed as respective pairsdisposed on opposing transverse sides of the slot 54 (see, e.g., FIG.13B)

The pusher 46 is disposed substantially within the handle 50 to slidewithin the chamber, and has a button 60 disposed on a top of a mainportion or beam 64 thereof, corresponding with the slot 54. Button 60has a projection or button stop 62 disposed on a side thereof. Accordingto one embodiment, projection 62 is one of a pair of projectionsdisposed on opposing sides of button 60. In use, the projection 62selectively engages the detents 56 and 58 to secure the pusher 46 (andthe blade 48, as will be discussed in greater detail below) in theblade-retracted and blade-extended positions. According to oneembodiment, as shown, for example, in FIG. 7A, the projection 62 isdesigned to ease disengagement with the detents 56 or 58. In operation,once the projection 62 is engaged with the one of the detents 56 or 58,the user depresses the button 60 (pushing inwardly with respect to thehandle 50) to disengage from the current detent. Then, the user slidesthe button 60 to advance it toward the target detent, and there is anaudible click, as the projection 62 snaps into the target detent, toconfirm positioning therein. According to another embodiment, the usermoves the button 60 sideways to disengage the projection from a detent,either 56 or 58, (thereby elastically deforming the projection 62 and/orthe handle 50) and slides the button 60 to advance it toward the targetdetent.

According to an alternative embodiment (not shown), the positioning ofthe detents and the projection is reversed, i.e., the slot 54 hasprojections corresponding, respectively, to the blade-extended andblade-retracted positions, and the button has a detent that selectivelyengages the projections.

FIG. 7A illustrates the pusher 46 of the safety knife 40. As shown inFIGS. 3 and 7A, a tilt beam 66 made of plastic, metal, or other rigid,but resilient material extends from an end of the main portion 64 of thepusher 46, and the blade 48 is connected with an end of the tilt beam66. The tilt beam has a tilt pin 70 disposed thereon. According to oneembodiment, the blade is connected with a first end of a head 68, and asecond end of the head, opposite to the first end, is connected with thetilt beam 66. The blade 48 can be connected with the head 68 in anydesired manner, e.g., by being glued, press fitted, snapped, screwed,and/or molded to the head 68. According to one embodiment, shown, forexample, in FIG. 7B, the head 68 is detachable from the tilt beam 66. Insuch an embodiment, the head 68 can be connected with the tilt beam 66by being glued, press fitted, snapped, and/or screwed to the tilt beam66.

FIG. 8A illustrates cutaway and end views of an end of the handle 50.FIG. 8B illustrates cutaway and end views of the pusher 46, the blade48, and the end of the handle 50 in the blade-extended and extendedpositions. FIG. 8C illustrates cutaway and end views of the pusher 46,the blade 48, and the end of the handle 50 in the blade-retracted andnested positions. FIG. 9A illustrates enlarged cutaway and end views ofthe pusher 46, the blade 48, and the end of the handle 50 between theblade-extended/extended positions and blade-retracted/nested positions.And FIG. 9B illustrates enlarged cutaway and end views of the pusher 46,the blade 48, and the end of the handle 50 in the blade-retracted andnested positions.

As shown in FIGS. 5A, 6B, and 8A, the handle 50 includes a tilt track72, which may alternately be referred to as a cam track or tilt slot.According to one embodiment, respective portions of the tilt track 72are molded in the base 44 and cover 42 during manufacture thereof.According to another embodiment, respective portions of the tilt track72 are milled in the base 44 and cover 42 during manufacture thereof.

The tilt track 72 defines an inclined (i.e., with respect to the handleaxis) guide path for the tilt pin 70. When the pusher 46 is assembledwithin the chamber of the handle 50, the tilt pin 70 is engaged withtilt track 72. According to one embodiment, the handle 50 has a pair oftilt tracks 72 on opposing sides of the chamber, to guide opposing endsof the tilt pin 70. As shown in FIGS. 8B and 8C, as the pusher 46 isretracted by a user, the tilt pin 70 is forced upward by riding in thetilt track 72. When the tilt pin 70 is forced up the tilt beam 66 isdeflected, that is, its shape is changed, such as by deformation(preferably elastic deformation) of the tilt beam 66, as shown in FIGS.8B and 8C. This causes the head 68 and blade 48 to rotate down. In otherwords, as the main portion 64 of the pusher 46 moves between theblade-extended and blade-retracted positions, the tilt pin travels inthe tilt track 72, deflecting the tilt beam 66, rotating the blade 48from the extended position to a nested position, and retracting theblade 48 within the handle 50. Conversely, as the main portion 64 of thepusher 46 moves between the blade retracted and blade-extendedpositions, the tilt pin travels in the tilt track 72, again deflecting(i.e., changing the shape of) the tilt beam 66, extending the blade 48from the handle 50, and rotating the blade 48 from the nested positionto the extended position.

FIGS. 9A and 9B respectively show the head 68 and the blade 48 in thenested position between the blade-extended and blade-retractedpositions, and in the blade-retracted/nested positions.

Referring back to FIG. 8A, the guide path of tilt track 72 preferablyincludes a first guide path portion 74 and a second guide path portion76. The first guide path portion 74 is inclined at an angle of about5-10° with respect to the substantially linear travel path of the mainportion 64 of the pusher 46. According to one embodiment, the firstguide path portion 74 is inclined at an angle of about 6.24° withrespect to the substantially linear travel path of the main portion 64of the pusher 46. The second guide path portion 76 adjoins the firstguide path portion 74 and is substantially parallel to the travel pathof the main portion 64. When the tilt pin 70 travels along the firstguide path portion 74, the blade 48 rotates with respect to the handle50 between the nested and extended positions, as well as translates withrespect to the handle 50. And when the tilt pin 70 travels along thesecond guide path portion 76, the blade 48 translates with respect tothe handle 50. Thus, moving the pusher 46 substantially linearly withinthe handle 50, between the blade-extended and blade-retracted positionsresults in both translational and rotational movement of the blade 48.

The shape of the tilt track 72 (and in the specific case of theembodiment of FIG. 8A, the angle of the first guide path portion 74)dictates how fast and far the head 68 and blade 48 move. Thus, accordingto the shape of the tilt track 72 of FIG. 8A, the tip of blade 48 divesdown towards the handle's 50 centerline during retraction. But it willbe appreciated that embodiments of the present invention are not limitedto the first and second guide paths 74 and 76 shown in FIG. 8A. Forexample, in the modified embodiment of FIG. 10, tilt track 72A iscurvilinear. When the tilt pin 70 travels along the tilt track 72A, theblade 48 rotates with respect to the handle 50 between the nested andextended positions, as well as translates with respect to the handle 50.

The blade 48 shown, for example, in FIGS. 3-9B, is depicted as being around stock blade about 3.2 mm in width and having a bend height ofabout 0.205 inches (about 5.2 mm). These are substantially the samedimensions as the blade 18 that is depicted in FIGS. 1, 2A, and 2B. Withthe retractable safety knife 40 however, as shown, e.g., in FIGS. 9A and9B, such a blade achieves a tip clearance 73 of about 0.039 inches and aside clearance 75 of about 0.031 inches when in the nested andblade-retracted/nested positions. Since a guard does not have to beaccommodated within the chamber of handle 50, even if an internaldiameter handle 50 is the same as that of handle 16, a larger blade canbe accommodated within handle 50. In fact, given the above notedclearances with respect to blade 48 and handle 50, a blade approximately4.0 mm wide, with a bend height increase of 0.02 inches (total of about0.225 inches) can be accommodated within handle 50. It will beunderstood that embodiments of the present invention are not limited tothe above-described blades, and that differently sized blades may beemployed. Additionally, it will be understood that flat stock blades maybe employed.

One issue that may generally arise with retractable knives is alooseness of the blade relative to the handle. For the user, this mayintroduce “play” into the tactile feedback. To combat this and provide auser with good tactile feedback, in the embodiment of the presentinvention shown in FIG. 8B, a portion of the head 68 has a cylindricaldiameter that has minimal clearance with respect to a bore of thechamber of the handle 50. Additionally, as shown in FIGS. 8A and 8B,when the pusher 46 is moved from the blade-retracted position to theblade-extended position, the tilt pin 70 crosses the longitudinalcenterline of the handle 50, tensioning the tilt beam 66.

Further, according to another embodiment, as shown in FIG. 11A, thehandle 50 has an annular groove 78, and the head 68 has an annularprotrusion 79. As the blade 48 reaches the extended position, theannular protrusion 79 positively engages the annular groove 78, tostabilize the blade 48 in the extended position. According to anotherembodiment shown in FIG. 11B, the handle 50 has the annular protrusion79 and the head 68 has the annular groove 78.

Yet further, according to one embodiment, as shown in FIGS. 12A 12E, themain portion 64 of the pusher 46 has a slot 80 therein extending along alongitudinal axis of the pusher 46, the slot having detents 82 and 84corresponding to the blade-extended and blade-retracted positions.Additionally, the handle 50 has an inwardly-directed alignment pin 86(see FIGS. 12B-12E) that is stationary and engages the pusher slot 80when the safety knife 40 is assembled. Beginning, for example, at theblade-retracted position (FIG. 12B), as the pusher 46 is moved (FIG.12C) to the blade-extended position (FIG. 12D), the slot 80 movesrelative to the alignment pin 86. When the pusher 46 is moved to theblade-extended position though (FIG. 12D), the alignment pin does notfully engage the detent 82, thereby creating a force that urges thepusher 46 toward the blade-extended position. In other words, when thepusher 46 is moved to the blade-extended position, as shown in FIG. 12D,a portion of the alignment pin 86 is still engaged with a constrictedportion of the slot 80 disposed between the detents 82 and 84. Becausethe constricted portion of the slot 80 elastically deforms duringrelative passage of the alignment pin 86 therethrough (as shown, forexample, in FIG. 12C), the portion of the alignment pin 86 still engagedwith the constricted portion of the slot 80 when the pusher 46 is movedto the blade-extended position elastically deforms the end of theconstricted portion adjacent to the detent 82. Thus, the constrictedportion of the slot 80 exerts a force relative to the alignment pin 86to bias the alignment pin 86 toward the detent 82, and thereby urge thepusher 46 toward the blade-extended position.

FIGS. 13A and 13B respectively illustrate related art safety knife 10and retractable safety knife 40 in position for a typical clear cornealincision. As can be seen in FIG. 13B, the configuration of retractablesafety knife 40 provides a clear view of the blade 48 for a surgeon,whereas in contrast, the enlarged distal end 28 of related art safetyknife 10 (FIG. 13A) may partially obscure the view of blade 18. And, asnoted previously, while the enlarged distal end 28 may be made of atransparent material, the curved surface may distort a surgeon's view ofthe blade 18.

Although only a few embodiments of the present invention have been shownand described, the present invention is not limited to the describedembodiments. Instead, it will be appreciated by those skilled in the artthat changes may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined bythe claims and their equivalents.

What is claimed is:
 1. An apparatus, comprising: a hollow handle havingan opening at an end thereof, the handle having a tilt track; a pushermovably disposed within the handle and operable by a user, the pushercomprising a main portion connected with a tilt beam, the tilt beamhaving a tilt pin disposed thereon; and a blade connected with an end ofthe pusher; wherein the tilt pin is engaged with the tilt track, thetilt track defining a guide path for the tilt pin; and wherein when thepusher moves from a blade-retracted position to a blade-extendedposition, the tilt pin moves in the tilt track to translate and extendthe blade from the handle during at least part of said tilt pin movementand to change the shape of the tilt beam, said change of shape causingrotation of the blade during at least part of said tilt pin movement. 2.The apparatus according to claim 1, wherein: the handle comprises asecond opening; and the pusher comprises a button extending through thesecond opening and slides between the blade-extended and blade-retractedpositions.
 3. The apparatus according to claim 2, wherein: the secondopening has a pair of detents corresponding, respectively, to theblade-extended and blade-retracted positions of the pusher; and thebutton comprises a projection audibly and positively engaging therespective detents when the pusher is moved to the blade-extended andblade-retracted positions.
 4. The apparatus according to claim 1,wherein the blade is connected with an end of the tilt beam.
 5. Theapparatus according to claim 1, wherein when the pusher is moved fromthe blade-extended position to the blade-retracted position, the tiltpin moves in the tilt track, changing the shape of the tilt beam,rotating the blade to a nested position, and retracting the blade intothe handle.
 6. The apparatus according to claim 1, wherein when thepusher is moved from the blade-retracted position to the blade-extendedposition, the tilt pin moves past a longitudinal centerline of thehandle, tensioning the tilt beam.
 7. The apparatus according to claim 1,further comprising a head, wherein the blade is connected with a firstend of the head, and a second end of the head connects with the pusher.8. The apparatus according to claim 7, wherein the head is detachablefrom the pusher.
 9. An apparatus, comprising: a hollow handle having anopening at an end thereof, the handle having a tilt track; a pushermovably disposed within the handle and operable by a user, the pushercomprising a main portion connected with a tilt beam, the tilt beamhaving a tilt pin disposed thereon; and a blade connected with an end ofthe pusher; wherein the tilt pin is engaged with the tilt track, thetilt track defining a guide path for the tilt pin; and wherein when thepusher moves from a blade-retracted position to a blade-extendedposition, the tilt pin moves in the tilt track to translate and extendthe blade from the handle during at least part of said tilt pin movementand to change the shape of the tilt beam to rotate the blade during atleast part of said tilt pin movement; wherein the guide path comprises:a first guide path portion that is inclined with respect to a travelpath of the main portion of the pusher; and a second guide path portionthat is substantially parallel to the travel path of the main portion ofthe pusher; wherein when the tilt pin travels along the first guide pathportion, the blade rotates with respect to the handle between nested andextended positions, and when the tilt pin travels along the second guidepath portion, the blade translates with respect to the handle.
 10. Anapparatus, comprising: a hollow handle having an opening at an endthereof, the handle having a tilt track; a pusher movably disposedwithin the handle and operable by a user, the pusher comprising a mainportion connected with a tilt beam, the tilt beam having a tilt pindisposed thereon; and a blade connected with an end of the pusher;wherein the tilt pin is engaged with the tilt track, the tilt trackdefining a guide path for the tilt pin; and wherein when the pushermoves from a blade-retracted position to a blade-extended position, thetilt pin moves in the tilt track to translate and extend the blade fromthe handle during at least part of said tilt pin movement and to changethe shape of the tilt beam to rotate the blade during at least part ofsaid tilt pin movement; wherein the main portion of the pusher has aslot therein extending along a longitudinal axis of the pusher, the slothaving at least one detent; wherein the handle comprises an alignmentpin corresponding with and being inserted into the pusher slot; andwherein when the pusher is moved from the blade-retracted position tothe blade-extended position, the alignment pin does not fully engage thedetent, creating a force that urges the pusher toward the blade-extendedposition.
 11. An apparatus, comprising: a hollow handle having anopening at an end thereof, the handle having a tilt track; a pushermovably disposed within the handle and operable by a user, the pushercomprising a main portion connected with a tilt beam, the tilt beamhaving a tilt pin disposed thereon; a blade connected with an end of thepusher; and a head; wherein the tilt pin is engaged with the tilt track,the tilt track defining a guide path for the tilt pin; and wherein whenthe pusher moves from a blade-retracted position to a blade-extendedposition, the tilt pin moves in the tilt track to translate and extendthe blade from the handle during at least part of said tilt pin movementand to change the shape of the tilt beam to rotate the blade during atleast part of said tilt pin movement; wherein the blade is connectedwith a first end of the head, and a second end of the head connects withthe pusher; wherein the handle has an annular groove; wherein the headhas an annular protrusion; and wherein as the blade reaches the extendedposition, the annular protrusion positively engages the annular groove,to stabilize the blade in the extended position.
 12. An apparatus,comprising: a hollow handle having an opening at an end thereof, thehandle having a tilt track; a pusher movably disposed within the handleand operable by a user, the pusher comprising a main portion connectedwith a tilt beam, the tilt beam having a tilt pin disposed thereon; ablade connected with an end of the pusher; and a head; wherein the tiltpin is engaged with the tilt track, the tilt track defining a guide pathfor the tilt pin; wherein when the pusher moves from a blade-retractedposition to a blade-extended position, the tilt pin moves in the tilttrack to translate and extend the blade from the handle during at leastpart of said tilt pin movement and to change the shape of the tilt beamto rotate the blade during at least part of said tilt pin movement;wherein the blade is connected with a first end of the head, and asecond end of the head connects with the pusher; wherein the head has anannular groove; wherein the handle has an annular protrusion; andwherein as the blade reaches the extended position, the annularprotrusion positively engages the annular groove, to stabilize the bladein the extended position.
 13. An apparatus, comprising: a hollow handlehaving an opening at an end thereof, and a tilt track; a pusher movablydisposed within the handle and operable by a user, the pusher comprisinga main portion connected with a tilt beam, the tilt beam having a tiltpin disposed thereon, the tilt pin engaging the tilt track; and a bladeconnected with an end of the tilt beam; wherein the tilt track defines aguide path for the tilt pin during extension and retraction of theblade, to change the shape of the tilt beam, rotate the blade relativeto the handle, and translate the blade relative to the handle; whereinthe guide path comprises: a first guide path portion that is inclinedwith respect to a travel path of the main portion of the pusher; and asecond guide path portion that is substantially parallel to the travelpath of the main portion of the pusher; wherein when the tilt pintravels along the first guide path portion, the blade rotates withrespect to the handle between the nested and extended positions, andwhen the tilt pin travels along the second guide path portion, the bladetranslates with respect to the handle.
 14. An apparatus, comprising: ahollow handle having an opening at an end thereof, and a tilt track; apusher movably disposed within the handle and operable by a user, thepusher comprising a main portion connected with a tilt beam, the tiltbeam having a tilt pin disposed thereon, the tilt pin engaging the tilttrack; and a blade connected with an end of the tilt beam; wherein thetilt beam is disposed between the blade and the main portion of thepusher; and wherein at least one of: when the pusher moves from ablade-extended position to a blade-retracted position, the tilt pinmoves in the tilt track, deforming the tilt beam and moving the blade intranslation and rotation to rotate the blade relative to the handle froman extended position to a nested position, and retract the blade intothe handle opening; and when the pusher moves from the blade-retractedposition to the blade-extended position, the tilt pin moves in the tilttrack, deforming the tilt beam and moving the blade in translation androtation to rotate the blade from the nested position to the extendedposition, and extend the blade out of the handle opening.
 15. Theapparatus according to claim 14, wherein the said opening comprises asubstantially circular opening.
 16. The apparatus according to claim 14,wherein the rotation and translation are substantially simultaneousduring at least part of said tilt pin movement.
 17. A method forshielding and exposing a blade in a surgical instrument, comprising:changing the shape of a member within said instrument to cause the bladeto rotate while translating, thereby moving the blade relative to ahandle of said instrument from an extended position to a nested positionand retracting the blade into a handle opening; and changing the shapeof the member within said instrument to cause the blade to rotate whiletranslating, thereby moving the blade from the nested position to theextended position and extending the blade out of the handle opening. 18.An apparatus, comprising: a hollow handle having an opening at an endthereof, the handle having a tilt track; a pusher movably disposedwithin the handle and operable by a user, the pusher comprising a mainportion connected with a tilt beam, the tilt beam having a tilt pindisposed thereon; the tilt pin being engaged with the tilt track, whichdefines a guide path for the tilt pin; and a blade connected with an endof the pusher, the blade being connected with an end of the tilt beam;wherein when the pusher moves from a blade-retracted position to ablade-extended position, the blade extends outwardly from the handleopening and rotates from a nested position to an extended position;wherein the main portion of the pusher has a slot therein extendingalong a longitudinal axis of the pusher, the slot has at least onedetent, and the handle comprises an alignment pin corresponding with andbeing inserted into the pusher slot; and wherein when the pusher ismoved from the blade-retracted position to the blade-extended position,the alignment pin does not fully engage the detent, creating a forcethat urges the pusher toward the blade-extended position.
 19. Anapparatus, comprising: a substantially cylindrical handle defining achamber therein and having at least one slot extending along alongitudinal axis accessing the chamber, the chamber being open at adistal end of the handle, the chamber having a tilt track disposedtherein defining a guide path; a pusher movably disposed within thechamber and having a control button protruding through the longitudinalhandle slot, the pusher comprising a main portion, the control buttonbeing attached thereto, and a tilt beam connected to the main portion,the tilt beam having a tilt pin disposed thereon, the tilt pin engagingthe tilt track and being guided along the guide path; and a bladeconnected with an end of the tilt beam; wherein moving the pushercontrol button between opposing ends of the longitudinal handle slottranslates the main portion of the pusher and moves the tilt pin alongthe guide path to change the shape of the tilt beam to cause the bladeto rotate while translating, thereby moving the blade between a nestedposition retracted within the chamber and an extended position externalto the chamber via the distal opening of the chamber.
 20. The apparatusaccording to claim 19, wherein the blade comprises a bent blade.